1. Field of the Disclosure
The present disclosure relates to the provision and use of videometry in various operations relating to the field of oil-well drilling, particularly offshore drilling operations. More particularly, the disclosure relates to a system for determining the position of a downhole drill pipe relative to a pipe handling device.
2. Background of the Technology
Videometry may take various forms but can generally be considered to relate to the use of optical sensing devices to automatically receive and interpret an image of a real scene, to obtain geometrical information, and to control directional information, the location or orientation of a component part, or simply the presence or absence of an object or component in a particular environment.
Turning now to consider more particularly the nature of oil field drilling operations themselves, it will be appreciated a drill string as is commonly run in a well bore is made up of a series of interconnected drill pipes. Additional pipes are added to the top of the string at successive stages in the drilling process as the string becomes longer, and hence deeper in the well. The reverse process occurs when a drill string is being retracted from a well.
When running a drill string into or out of a well bore, a combination torque wrench and spinning wrench is typically used for connecting and disconnecting adjacent drill pipes and/or pre-assembled stands. In this context, a stand is a number (typically two to four) of preassembled drill pipes which are stored in an intermediate storage rack until such time as they are required to be added to a drill string as it is run into a well.
Such combination torque wrenches and spinning wrenches are commonly known as “iron roughnecks”. It is important to ensure that the iron roughneck is positioned at the correct height relative to the joint to be made up or broken. As tool joints often vary in terms of diameter or length, instrumentation to achieve this has been found to be unsatisfactory and so height positioning is generally done manually. Additionally, not all of the drill pipes used in a typical string are of exactly equal length, and also the height of the uppermost pipe in a string sticking up out of the well bore between successive drilling (or hoisting) stages, which is commonly known as the “stick-up height”, will be slightly different each time.